Information Technology Services

Troubleshooting VPN Issues

1. What can I do if my VPN connection is slow or randomly drops the connection, stating “Remote Peer No Longer Responding”?
   
   This could be due to network latency. To improve performance, you can adjust the Maximum Transfer Unit (MTU) and encapsulation settings. Here is a short guide to tuning the performance of your VPN client:
   • Change your MTU: Setting your MTU to 1300 or lower will prevent packets from being fragmented and therefore increase performance. To change your MTU, click on the Start menu. Select All Programs and Cisco Systems VPN Client. Then select Set MTU. Once you set your MTU on a network interface, it will ask you to reboot your computer.
   • Disable encapsulation*: If you have a unique IP address, you can disable encapsulation. For example, if you are on a cable modem network or dial-up connection with no hardware-based firewall, you can safely disable all encapsulation. To disable encapsulation, modify your current VPN profile (Highlight it and click the Modify button), go to the Transport tab, then uncheck Enable Transparent Tunneling.
     
     *Encapsulation allows for two people with the same IP address to connect via the VPN. This can occur if you have two people who both have Linksys firewalls and accept the default IP address given by the firewall (usually 192.168.1.100). TCP encapsulation also works well if you are behind a firewall that only allows ports 80 and 443 outgoing (443 is UNCG's default port for IPSec over TCP). If you are on UNCG's wireless network you can safely disable encapsulation.
   • Check with your Internet Service Provider (ISP) - VPN connections are especially sensitive to network latency (the time it takes a packet to get from one host to another). Your cable modem or cable infrastructure may be experiencing problems that cause latency. Your provider can come check the lines and possibly replace your cable modem to improve the situation.
     
     Note: Latency is different from bandwidth. Bandwidth is a measure of how much information can be sent, not how fast. Options for increasing your bandwidth are available from most ISPs at an extra cost. A bandwidth upgrade will improve your download speeds, but not help your VPN connection.
2. I am using AOL and I am unable to connect to the VPN. Why does this happen?
   
   Certain versions of AOL work with certain versions of the Cisco VPN client. However, AOL has a long history of causing problems for VPN connections (it replaces key system files) and is therefore unsupported for UNCG VPN connections.
   
   
3. I am behind a VPN-aware firewall and I get disconnected after less than 30 minutes of idle time. Why does this happen?
   
   Certain vendors' firewalls are known to cause timeout problems when the client is idle. The problem occurs when the client cannot send the proper “keepalive” messages back to the VPN concentrator. If this is happening, then not being idle will prevent you from being disconnected. Opening an application that sends data constantly [such as Outlook or a Secure Shell (SSH) terminal window] will prevent your connection from being idle. If the idle timeout is still a problem, please contact your vendor for a workaround or patch.
   
   
4. I get the one of the following error messages. What could be causing this?
   • "Secure VPN Connection terminated locally by the Client. Reason 413: User authentication failed."
     
   • "The necessary VPN sub-system is not available. You cannot connect to the remote VPN server."
   You could have made changes in the default Authentication settings (Authentication tab).  If you have changed any of these settings, you will need to reinstall the client and obtain necessary group authentication credentials by calling 6-TECH Technical Support at 336-256-TECH (8324).  If you are repeatedly prompted for your password, go to the Self Service Password Resetting form to reset your Novell NDS password.
   
   
5. When using VPN from home with XP Pro SP2, my connection terminates and I receive the error message “413 user authentication failed.” Is there a fix for this?
   
   Uninstall the VPN client and then reinstall it.